1. Field of the Invention
The present invention relates to a linear measuring machine having a probe movable vertically, the probe being in contact with a target portion of a workpiece to measure a workpiece dimension such as height, level difference, hole and shaft.
2. Description of Related Art
Conventionally, a linear measuring machine having a probe movable vertically, the probe being in contact with a target portion of a workpiece to measure a workpiece dimension such as height, level difference, hole and shaft, has been known in, for example, a linear distance measuring machine disclosed in Japanese Patent Application Laid-Open Publication No. Hei 6-123602.
The linear measuring machine has a base, a column mounted on the base, a first slider vertically ascendable and descendable along the column and having a probe to be in contact with a workpiece, a displacement sensor for detecting a height position of the first slider, a second slider provided to the first slider movable in the same direction as a moving direction of the first slider, a constant-pressure mechanism for holding the first slider relative to the second slider, the constant-pressure mechanism relatively moving the second slider relative to the first slider when a more than predetermined load is applied between the sliders and returning the first slider and the second slider to a rest position when the load is released, a drive mechanism connected to the second slider for lifting and lowering the first and the second slider along the column upwardly and downwardly, and a switch actuated when the second slider moves relative to the first slider to capture a detection value of the displacement sensor.
In initiating measurement, the drive mechanism is actuated to lift and lower the first and the second slider vertically along the column. When the probe is in contact with the workpiece, since the first slider cannot move further, the second slider moves relative to the first slider. Then, the switch is actuated to capture the detection value of the displacement sensor. In other words, a height position of the first slider when the probe touches the workpiece is detected. Accordingly, the dimension of the workpiece can be measured by sequentially measuring a target portion of the workpiece.
[First Problem]
In the above-described measuring machine, since the detection value of the displacement sensor is captured by actuating the switch when the second slider moves relative to the first slider after the probe touches the workpiece, the detection value of the displacement sensor can be captured while impulse or vibration caused when the probe touches the workpiece is not stilled.
When the detection value is captured during the above condition, the detection value of the displacement sensor is unstable on account of influence of the impulse of the vibration, which can be observed as a measurement error.
[Second Problem]
As the switch of the measuring machine, an arrangement having a resistance band provided on the first slider along the moving direction thereof and a plate spring provided on the second slider with an end thereof sliding on the resistance band has been known, where the switch is actuated when a resistance value of the resistance band up to a position where the plate spring touches the resistance band reaches a predetermined value, thereby capturing the detection value of the displacement sensor.
However, since the plate spring slides on the resistance band according to the switch arrangement, the resistance value is likely to be fluctuated on account of the slide movement. In other words, such arrangement is likely to be influenced by age deterioration.
[Third Problem]
Since the constant-pressure mechanism of the aforesaid linear distance measuring machine is composed of three coil springs, more specifically, first extension coil spring for balancing weight of the first slider itself and two mutually parallel second extension coil springs opposing in motion for maintaining constant measuring pressure on both moving directions of the second slider, a space for disposing the coil springs in mutually parallel manner has to be secured in width direction of the slider. Further, since the extension coil spring requires considerable longitudinal space, the size of the slide portion can be increased.
Further, when two extension coil springs are used for maintaining the constant measuring pressure, extension coil springs are actuated when the second slider is lifted and when the second slider is lowered. Accordingly, since the measurement pressure when the second slider is lifted and the measurement pressure when the second slider is lowered become different if the spring pressures of the two extension coil springs are identical, so that the measuring pressure can be different according to measurement direction.
[Fourth Problem]
Since the constant-pressure mechanism of the aforesaid linear distance measuring machine is composed of three coil springs, more specifically, first extension coil spring for balancing weight of the first slider itself and two mutually parallel second extension coil springs opposing in motion for maintaining constant measuring pressure on both moving directions of the second slider, the first slider having the probe is likely to move along the column when an outside force is applied to the probe. Therefore, it is difficult to conduct marking-off work with the conventional linear distance-measuring machine.
Further, when impulse or vibration is applied during transportation, the first slider moves along the column, so that the three coil springs can be excessively stretched.
[First Aspect]
For solving the aforesaid first problem, first aspect of the present invention includes following arrangement including: a base; a column mounted on the base; a first slider movable vertically along the column and having a probe to be in contact with a workpiece; a displacement sensor for detecting height position of the first slider; a second slider provided on the first slider, the second slider being movable in the same direction as a moving direction of the first slider; a constant-pressure mechanism for holding the first slider against the second slider, the constant-pressure mechanism moving the second slider relative to the first slider when a more than predetermined load is applied between the sliders and returning the first slider and the second slider to a rest position when the load is released; a drive mechanism connected to the second slider for vertically moving the second slider along the column; and a switch being actuated when the second slider moves relative to the first slider to capture a detection value of the displacement sensor, the linear measuring machine being characterized in that an allowable relative movement amount of the first slider and the second slider is not less than 3 mm, and that the switch is actuated to capture the detection value of the displacement sensor when the first slider and the second slider relatively move not less than 3 mm.
According to the above arrangement, when the second slider is vertically lifted and lowered along the column, lowered for instance, the first slider is also lowered together in the same direction by the constant-pressure mechanism. Then, when the second slider is further lowered after the probe touches the workpiece, since the first slider cannot be further lowered, the second slider is moved (lowered) relative to the first slider by the constant-pressure mechanism when the more than predetermined load is applied between the first and the second sliders. When the relative movement amount is not less than 3 mm, the switch is actuated to capture the detection value of the displacement sensor. In other words, the height dimension of the measurement surface of the workpiece in contact with the probe is measured (basic movement).
Accordingly, since the detection value of the displacement sensor is captured when the second slider is moved relative to the first slider for not less than 3 mm, the impulse or the vibration caused when the probe touches the workpiece is stilled, thus enabling stable measurement. In other words, the dimension of the workpiece can be accurately measured without being influenced by the impulse or the vibration when the probe touches the workpiece.
In the first aspect of the present invention, the allowable relative movement amount of the first slider and the second slider may preferably be not less than 3 mm, where, during ordinary measurement, the switch may preferably be actuated when the first slider and the second slider relatively move not less than 3 mm to capture the detection value of the displacement sensor, and where, during profiling measurement, the switch may preferably be actuated when the first slider and the second slider relatively move not less than 3 mm to capture the detection value of the displacement sensor, and, thereafter, the detection value of the displacement sensor may preferably be captured at a predetermined time interval.
In the above arrangement, the workpiece is measured according to the same function as described thus far during normal measurement.
On the other hand, during profiling measurement, the workpiece is measured as follows. For instance, during profiling measurement of the inner circumference of a hole of the workpiece, the second slider is vertically moved, lowered for instance, along the column, so that the first slider is lowered together in the same direction through the constant-pressure mechanism. Then, after the probe touch the inner wall of the hole of the workpiece, the second slider is further lowered. Since the first slider cannot be further lowered, the second slider is moved (lowered) relative to the first slider by the constant-pressure mechanism when a more than predetermined load is applied between the first and the second sliders. When the relative movement becomes not less than 3 mm, the switch is actuated to capture the detection value of the displacement sensor.
Since the second slider is lowered for not less than 3 mm relative to the first slider under the above state, downward force is applied to the first slider and the probe by the constant-pressure mechanism. Accordingly, when the workpiece or the linear measuring machine is horizontally moved under the above state, the detection value of the displacement sensor is captured at a predetermined time interval. In other words, since the detection value of the displacement sensor can be captured at the predetermined time interval while the probe relatively moves keeping in contact with and profiling the inner wall of the hole, the value of the lowermost end of the hole can be obtained by calculating the minimum value of the captured detection value.
In the first aspect of the present invention, the switch may preferably further include: a first contact pin and a second contact pin on either one of the first and the second sliders mutually spaced apart along a moving direction of the sliders; a swing lever swingably supported by the other one of the first and the second sliders, a part of the swing lever remote from a swing support point thereof being located at the center of the first contact pin and the second contact pin; and a biasing means for retaining the swing lever at a rest condition and for allowing a swing movement of the swing lever during relative movement of the first and the second sliders, the gap between the swing lever and the first contact pin and the gap between the swing lever and the second contact pin being not less than 3 mm at the rest position of the swing lever.
According to the above arrangement, when the second slider is moved (lowered) relative to the first slider after the probe touches the workpiece, the swing lever and the first or the second contact pin touch with each other when the relative movement amount becomes not less than 3 mm. Then, the detection value of the displacement sensor at the time is captured. In other words, the height dimension of the measurement surface of the workpiece in contact with the probe can be measured.
When the second slider is further moved (lowered) relative to the first slider, since the swing lever is swung while being in contact with the first or the second contact pin, the damage and failure of the swing lever and the first and the second contact pins can be prevented, which also contribute to protection of the probe.
After measurement, when the second slider is lifted along the column by the drive mechanism, the swing lever is separated from the first or the second contact pin while being gradually returning to the rest position by virtue of the biasing means. When the second slider is further lifted, the first slider and the second slider return to the rest position while gradually releasing the load applied between the first and the second sliders. In other words, the second slider returns to the rest position of the first slider.
Accordingly, since the first and the second contact pin and the swing lever constituting the switch only temporarily touch with other during measurement accompanying relative movement of the first and the second sliders, the influence of age deterioration can be substantially decreased as compared to the arrangement for detecting the relative movement of the sliders with a plate spring sliding on a resistance band. Further, since the switch can be composed of the first and the second contact pins, the swing lever and the biasing means, the relative displacement of both of the sliders can be securely detected with a simple arrangement.
In the above first aspect of the present invention, the biasing means may preferably include a single extension coil spring.
According to the above arrangement, since the biasing means is composed of a single extension coil spring, the biasing means can be constructed extremely inexpensively and construction thereof can be facilitated. Further, since the reaction force in swinging the swing lever after the swing lever is in contact with the first or the second contact pin can be adjusted by selecting spring force of the extension coil spring, an appropriate braking function can be endowed in lifting and lowering the second slider.
[Second Aspect]
For solving the aforesaid second problem, second aspect of the present invention has the following arrangement including: a base; a column mounted on the base; a first slider movable vertically along the column and having a probe to be in contact with a workpiece; a displacement sensor for detecting height position of the first slider; a second slider provided to the first slider, the second slider being movable in the same direction as a moving direction of the first slider; a constant-pressure mechanism for holding the first slider against the second slider, the constant-pressure mechanism moving the second slider relative to the first slider when a more than predetermined load is applied between the sliders and returning the first slider and the second slider to an initial position when the load is released; a drive mechanism connected to the second slider for vertically moving the second slider along the column; and a switch being actuated when the second slider moves relative to the first slider to capture a detection value of the displacement sensor; the switch further including: a first contact pin and a second contact pin on either one of the first and the second sliders mutually spaced apart along a moving direction of the slider; a swing lever swingably supported on the other one of the first and the second sliders, a part of the swing lever remote from a swing support point thereof being located at the center of the first contact pin and the second contact pin; and a biasing means for retaining the swing lever at a rest condition and for allowing a swing movement of the swing lever during relative movement of the first and the second sliders.
According to the above arrangement, the height dimension of the measurement surface in contact with the probe can be measured according to the basic movement described in the above first aspect of the present invention.
Further, when the second slider is further moved (lowered) relative to the first slider, since the swing lever is swung while being in contact with the first or the second contact pin, the damage and failure of the swing lever and the first and the second contact pins can be prevented, which also contribute to protection of the probe.
After measurement, when the second slider is lifted along the column by the drive mechanism, the swing lever is separated from the first or the second contact pin while gradually returning to the rest condition by virtue of the biasing means. When the second slider is further lifted, the first and the second sliders returns to the rest position while gradually releasing the load applied between the first and the second sliders. In other words, the second slider returns to the rest position of the first slider.
Accordingly, since the first and the second contact pin and the swing lever constituting the switch only temporarily touch with other during measurement accompanying relative movement of the first and the second sliders, the influence of age deterioration can be substantially decreased as compared to the arrangement for detecting the relative movement of the sliders with a plate spring sliding on a resistance band. Further, since the switch can be composed of the first and the second contact pins, the swing lever and the biasing means, the relative displacement of both of the sliders can be securely detected with a simple arrangement.
In the above second aspect of the present invention, a switching portion may preferably be formed between the first contact pin and the swing lever and between the second contact pin and the swing lever.
According to the above arrangement, since the switching portion is directly formed between the first contact pin and the swing lever and between the second contact pin and the swing lever, a separate switch is not necessary, thus reducing the number of parts and production cost.
In the above second aspect of the present invention, an intermediate portion of the swing lever may preferably be swingably supported by the other one of the first and the second sliders and one end of the swing lever may preferably be located at the center of the first contact pin and the second contact pin at the rest condition, and the biasing means may preferably include a single extension coil spring for stretching the other end of the swing lever perpendicularly relative to a straight line connecting the first contact pin and the second contact pin.
According to the above arrangement, since the biasing means is composed of a single extension coil spring, the biasing means can be constructed extremely inexpensively and construction thereof can be facilitated. Further, since the reaction force in swinging the swing lever after the swing lever is in contact with the first or the second contact pin can be adjusted by selecting spring force of the extension coil spring, an appropriate braking function can be endowed in lifting and lowering the second slider.
[Third Aspect]
For solving the aforesaid third problem, third aspect of the present invention has the following arrangement, including: a base; a column mounted on the base; a first slider movable vertically along the column and having a probe to be in contact with a workpiece; a displacement sensor for detecting height position of the first slider; a second slider provided to the first slider, the second slider being movable in the same direction as a moving direction of the first slider; a constant-pressure mechanism for holding the first slider against the second slider, the constant-pressure mechanism moving the second slider relative to the first slider when a more than predetermined load ;is applied between the sliders and returning the first slider and the second slider to an initial position when the load is released; a drive mechanism connected to the second slider for vertically moving the second slider along the column; and a switch being actuated when the second slider moves relative to the first slider to capture a detection value of the displacement sensor; the constant-pressure mechanism further comprising: a weight-balancing biasing means provided between the first slider and the second slider to bias the first slider upwardly with a force equal to a total weight of the first slider and a component attached to the first slider; a cam member provided to the first slider swingably in up and down direction and having a longitudinally-extending slide groove; an engage pin provided to the second slider to slidably engage the slide groove of the cam member; and a constant-pressure biasing means for allowing swing movement of the cam member when a more than predetermined force is applied between the first and the second slider in a relative movement direction thereof.
According to the above arrangement, the height dimension of the measurement surface of the workpiece in contact with the probe can be measured according to basic movement described in the first aspect of the present invention.
At this time, when a more than predetermined force is applied between the first and the second sliders in relative movement direction thereof, the cam member is swung against the constant-pressure biasing means and the second slider is moved relative to the first slider.
In other words, when the second slider is lowered relative to the first slider, since measurement pressure stays constant by the constant-pressure biasing means, the measurement pressure can be maintained constant irrespective of difference among individuals.
On the other hand, when the second slider is lifted by the drive mechanism, since only the cam member is swung upwardly against the constant-pressure biasing means, the measurement pressure in lifting the second slider and the measurement pressure in lowering the second slider can be made identical. In other words, the measurement pressure does not differ irrespective of measurement direction.
Incidentally, when the second slider is lifted along the column by the drive mechanism after measurement, the cam member gradually returns to the horizontal rest position.
Since the constant-pressure mechanism for conducting the above function is composed of the weight-balancing biasing means, a cam member, an engage pin and a constant-pressure biasing means, the size thereof can be reduced as compared to a conventional arrangement having parallel three extension coil springs extending along predetermined length.
Further, since the second slider is biased by the constant-pressure biasing means in being lifted and lowered, the measurement pressure in lifting the second slider and the measurement pressure in lowering the second pressure can be made identical.
In the above third aspect of the present invention, one end of the cam member may preferably be swingably supported by the first slider and the other end of the cam member may preferably be horizontally biased by the constant-pressure biasing means sandwiching the engage pin.
According to the above arrangement, since the tensile force is applied to the other end of the cam member with the one end of the cam member being the swing support point sandwiching the engage pin, returnability into the rest position can be highly maintained.
A linear measuring machine according to third aspect of the present invention may preferably include: a base; a column mounted on the base; a first slider movable vertically along the column and having a probe to be in contact with a workpiece; a displacement sensor for detecting height position of the first slider; a second slider provided to the first slider, the second slider being movable in the same direction as a moving direction of the first slider; a constant-pressure mechanism for holding the first slider against the second slider, the constant-pressure mechanism moving the second slider relative to the first slider when a more than predetermined load is applied between the sliders and returning the first slider and the second slider to an initial position when the load is released; a drive mechanism connected to the second slider for vertically moving the second slider along the column; and a switch being actuated when the second slider moves relative to the first slider to capture a detection value of the displacement sensor; the constant-pressure mechanism further comprising: a weight-balancing biasing means provided between the first slider and the second slider to bias the first slider upwardly with a force equal to a total weight of the first slider and a component attached to the first slider; a pair of plate spring disposed on either one of the first and the second sliders elastically deformable in a relative movement direction of the first and the second sliders; and a pair of press pin in contact with an elastically deformable portion of the respective plate springs, the pair of press pin being disposed on the other one of the first and the second sliders.
According to the above arrangement, the height dimension of the measurement surface of the workpiece in contact with the probe can be measured according to the basic movement described in the first aspect of the present invention.
At this time, as described above, since the measurement pressure stays constant on account of the constant-pressure biasing means in the constant-pressure mechanism, the measurement pressure can be maintained constant irrespective of difference among individuals and deviation in the measurement pressure can be reduced irrespective of measurement direction.
Further, since the constant-pressure mechanism is composed of the weight-balancing biasing means, the pair of plate spring, and the pair of press pin, the size of the constant-pressure mechanism can be reduced as compared to the arrangement having parallel three extension coil springs extending along predetermined length.
In the above third aspect of the present invention, the linear measuring machine may preferably include a single spring pressure adjustment means for simultaneously adjusting a spring pressure of the pair of the plate spring.
According to the above arrangement, since the spring pressure of the pair of plate spring can be simultaneously adjusted by the single spring pressure adjustment means, the adjustment work can be facilitated and the adjustment means can be economically constructed.
In the third aspect of the present invention, the linear measuring machine may preferably include two spring pressure adjustment means for independently adjusting the spring pressure of the pair of plate spring.
According to the above arrangement, since the spring pressure of the pair of plate spring can be simultaneously adjusted, the pressure can be easily corrected when, for instance, the measurement pressure in lifting the second slider and the measurement pressure in lowering the second slider differ.
[Fourth Aspect]
For solving the above fourth problem, fourth aspect of the present invention includes following arrangement.
A linear measuring machine according to fourth aspect of the present invention includes: a base; a column mounted on the base; a first slider movable vertically along the column and having a probe to be in contact with a workpiece; a displacement sensor for detecting height position of the first slider; a second slider provided to the first slider, the second slider being movable in the same direction as a moving direction of the first slider; a constant-pressure mechanism for holding the first slider against the second slider, the constant-pressure mechanism moving the second slider relative to the first slider when a more than predetermined load is applied between the sliders and returning the first slider and the second slider to an initial position when the load is released; a drive mechanism connected to the second slider for vertically moving the second slider along the column; a switch being actuated when the second slider moves relative to the first slider to capture a detection value of the displacement sensor; and a clamp mechanism for combining the first slider and the second slider.
According to the above arrangement, since the first slider and the second slider can be combined by the clamp mechanism, the position of the probe provided on the first slider can be fixed by combining the first slider and the second slider after fixing the second slider by fixing the drive mechanism. Accordingly, for instance, marking-off work can be conducted by exchanging the probe with a scriber etc. and horizontally moving the workpiece and/or the linear measuring machine while pressing the scriber onto the workpiece.
Further, during transportation, relative movement between the first and the second sliders can be prevented by combining the first slider and the second slider, so that trouble toward the constant-pressure mechanism interposed therebetween can be substantially reduced.
In the above fourth aspect of the present invention, the clamp mechanism may preferably include a through-hole provided on the second slider, an engage hole provided on the first slider correspondingly to the through-hole, and a clamp pin passing through the through-hole to engage the engage hole.
According to the above arrangement, since the first slider and the second slider can be combined by inserting the clamp pin into the through-hole of the second slider to engage with the engage hole of the first slider, an object of the present invention can be attained with a simply-structured clamp mechanism.
In the above fourth aspect of the present invention, the clamp mechanism may preferably further include a through-hole provided on the second slider, an engage hole provided on the first slider correspondingly to the through-hole, a clamp pin passing through the through-hole to engage the engage hole, and a clamp pin advance retainer for holding the clamp pin to the through-hole on the second slider and for advancing the clamp pin toward the engage hole when the clamp pin is rotated by a predetermined angle.
According to the above arrangement, since the clamp pin can be advanced toward and engaged with the engage hole of the first slider only by rotating for a predetermined angle after being retained in the through-hole on the second slider, the clamp pin can be easily secured to the first and the second sliders with shorter time as compared to an arrangement where, for instance, a screw hole is cut in the second slider and the clamp pin is screwed thereto for advancing the clamp pin toward the engage hole. Further, the clamp pin can be prevented from being fallen off from the first and the second sliders during marking-off work or transportation on account of the clamp pin advance retainer.
In the above fourth aspect of the present invention, the clamp pin advance retainer may preferably include: a positioning pin projecting perpendicularly from the clamp pin; a guide cylinder provided adjacent to the through-hole of the second slider and having a groove for the positioning pin to be engaged; and a biasing means for biasing the clamp pin in a direction for the clamp pin to advance toward the engage hole.
According to the above arrangement, since the clamp pin can be advanced with the positioning pin running along the groove of the guide cylinder, the clamp pin can be advanced along a central axis of the through-hole and the engage hole and toward the engage hole, so that the distal end of the clamp pin can be easily engaged with the engage hole.
In the above fourth aspect of the present invention, the distal end of the clamp pin may preferably be formed in tapered shape.
According to the above arrangement, since the distal end of the clamp pin is formed in tapered shape, even when mutual position between the central axis of the clamp pin inserted to the through-hole of the second slider and the center of the engage hole of the first slider is slightly shifted, the clamp pin can be securely inserted to the engage hole of the first slider.